The present invention relates to indicators used in combination with body fluid absorbent articles such as disposable diapers and making it visually perceivable whether a body fluid absorbent core of the articles is in a wet state or not. The present application is based on, and claims priority from, Japanese Application Serial Number 2002-380202,filed Dec. 27, 2002, the disclosure of which is hereby incorporated by reference in it's entirety.
Various indicators have already been well known, which generally intend to make it visually perceivable from outside a backsheet of a body fluid absorbent article whether urination has occurred or not. For example, an indicator disclosed in Japanese Patent Application Publication No. 1997-299401A is interposed between the backsheet and the body fluid absorbent core. This indicator comprises an ink layer adapted to be observable as this layer is wetted and an ink carrying layer interposed between the ink layer and the backsheet so as to be held in close contact with the ink layer. The ink carrying layer contains a surfactant. The above-cited Publication discloses an embodiment of the indicator in which the ink carrying layer is made of paper materials and, in addition to the first ink layer, a second ink layer is provided.
In the case of the known indicator using a water-absorbent paper as the ink supporting layer on which the ink layer is formed by printing, the water-absorbent paper is required to keep a sufficient dimensional stability and strength during a step of printing as well as during various steps of making diaper. To meet such requirements, the water-absorbent paper used for this application has usually been apt to have a basis weight and a bending stiffness both higher than those of nonwoven fabrics and plastic films used as stock materials for the top- and backsheets, respectively, of the diaper. Such paper interposed between the backsheet and the core inevitably makes a region of the backsheet overlapping the absorbent paper relatively stiff. Sometimes, such relatively stiff backsheet may deteriorate a desired soft touch for the wearer. Furthermore, the water-absorbent paper used for such purpose generally allows the amount of urine absorbed thereby to spread easily in this paper. However, information a mother wishes to acquire is not limited to the information whether urination has occurred or not. The other important information the mother wishes to acquire is how many repeated urinations have occurred and how wide range of the core has been wetted. On the basis of such information, the mother may determine to exchange the used diaper with a fresh diaper. With the indicator made of paper, the wetted range of the core does not often coincide with the wetted range of the indicator and it is difficult to specify the range of the core that is actually wetted on the basis of the wetted range of the indicator. Thus, the known indicator can not sometimes provide the adequate information the mother wishes to acquire.